In a distribution channel such as product shipping, a styroform packing material has been used for packing commodity and industrial products. Although the styroform package material has a merit such as a good thermal insulation performance and a light weight, it has also various disadvantages: recycling the styroform is not possible, soot is produced when it burns, a flake or chip comes off when it is snagged because of it's brittleness, an expensive mold is needed for its production, and a relatively large warehouse is necessary to store it.
Therefore, to solve such problems noted above, other packing materials and methods have been proposed. One method is a fluid container of sealingly containing a liquid or gas such as air (hereafter “air-packing device”). The air-packing device has excellent characteristics to solve the problems involved in the styroform. First, because the air-packing device is made of only thin sheets of plastic films, it does not need a large warehouse to store it unless the air-packing device is inflated. Second, a mold is not necessary for its production because of its simple structure. Third, the air-packing device does not produce a chip or dust which may have adverse effects on precision products. Also, recyclable materials can be used for the films forming the air-packing device. Further, the air-packing device can be produced with low cost and transported with low cost.
FIG. 1 shows an example of air-packing device in the conventional technology. The air-packing device 10a is composed of first and second thermoplastic films 13 and 14, respectively, and a check valve 11. Typically, each thermoplastic film is composed of three layers of materials: polyethylene, nylon and polyethylene which are bonded together with appropriate adhesive. The first and second thermoplastic films 13 and 14 are heat-sealed together around rectangular seal portions 12a, 12b to air-tightly close after the check valve 11 is attached. Thus, one air-packing device 10a sealed with the heat seal portions 12a, 12b is formed as shown in FIG. 1.
FIGS. 2A–2B show another example of an air-packing device 10b with multiple air containers where each air container is provided with a check valve. A main purpose of having multiple air containers is to increase the reliability. Namely, even if one of the air containers suffers from an air leakage for some reason, the air-packing device can still function as a cushion or shock absorber for protecting a product because other air containers are intact.
With reference to FIG. 2A, this fluid container 10b is made of the first and second thermoplastic films which are bonded together around a rectangular periphery 23a and further bonded together at each boundary of two air containers 22 so that a guide passage 21 and air containers 22 are created. When the first and second thermoplastic container films are bonded together, as shown in FIG. 2A, the check valves 11 are also attached to each inlet port of the air container 22. By attaching the check valves 11, each air container 22 becomes independent from the other. The inlet port 24 of the air-packing device lob is used when filling a fluid (typically air) to each air container 22 by using, for example, an air compressor.
FIG. 2B shows the air-packing device 10b of FIG. 2A when inflated with the air. First, each air container 22 is filled with the air from the inlet port 24 through the guide passage 21 and the check valve 11. To avoid a rupture of the air containers by variations in the environmental temperature, the air into the container is typically stopped when the air container 22 is inflated at about 90% of its full expansion rate. After filling the air, the expansion of each air container is maintained because each check-valve 11 prevents the reverse flow of the air. Typically, an air compressor has a gauge to monitor the supplied air pressure, and automatically stops supplying the air to the air-packing device 10b when the pressure reaches a predetermined value.
The check valve 11 is typically made of two rectangular thermoplastic valve films which are bonded together to form a fluid pipe. The fluid pipe has a tip opening and a valve body to allow a fluid flowing through the fluid pipe from the tip opening but the valve body prevents the reverse flow. Examples of structure of check-valve are described in more detail in the U.S. Pat. Nos. 5,209,264, 5,927,336 and 6,629,777. This check valve is attached to the thermoplastic films of the air packing device during or after the manufacturing process of the air-packing device.
As shown in FIGS. 2C–2E, the conventional check valves have problems. For example, when the air-packing device 10b is inflated, both sides 23a and 23b of the check valve body is pressed inwardly by the expansion of the air container 22. The directions of the pressing force is shown by arrows 25 in FIG. 2C. As a result, the check valves 11 become wavy such as shown in FIG. 2D although the bonded portion was straight before the air-packing device 10b is inflated.
As mentioned above, the check valve 11 is typically made of two thermoplastic films. By the pressure noted above, sometimes, a gap is created between the thermoplastic films 11a and the check-valve 11 of the air container 22. Thus, the air is leaked through the gap as shown in FIG. 2E where the leakage in the check valve 11a is shown by an arrow 27. In other words, the reverse flow in the air container by the check valve 11a occurs and the air from the air container 22 flows into the guide passage 21 in this example.
When using the check valves describe above, the pressure required to fill the fluid container can be large because when the air container is long and the guide passage 21 is narrow. This is especially true when each air container is configured by a plurality of air cells connected in series because the air has to be supplied from one end to another end of the air-packing device through many air cells. This can be a problem when the air compressor does not have much power to supply air with high pressure, or the part of the air-packing device closer to the air input may be damaged.
Still other problem with regard to the air-packing device having the conventional check valves described above lies in the inflexibility in mounting the check valve. As shown in FIGS. 2A–2B, the check valves 11 must be positioned adjacent to the guide passage 21, i.e. the air inlet port 24. Because the guide passage 21 must be positioned at the very end of the air-packing device 10b, freedom of designing the shape of the air-packing devices is severely limited.
As described in the foregoing, the air-packing device using the check valves is highly useful for packing commodity products and industrial products instead of the styroform packing. However, the conventional check valves have the problems as described above. Thus, there is a strong need for a check valve that can solve the above noted problems and an air-packing device implementing the new check valves.